In recent years, hybrid vehicles and electric vehicles have been attracting attention as environmentally-friendly vehicles. A hybrid vehicle is a vehicle powered by a direct current (DC) power supply, an inverter, and a motor driven by the inverter, in addition to a conventional engine. Specifically, the hybrid vehicle is powered by driving the engine, and is also powered by converting DC voltage from the DC power supply by the inverter into alternating current (AC) voltage and rotating the motor by the converted AC voltage.
Additionally, an electric vehicle is a vehicle powered by a DC power supply, an inverter, and a motor driven by the inverter.
In such a hybrid vehicle or an electric vehicle, to improve energy efficiency while allowing the vehicle to run appropriately, it is needed to supply electric power according to a load on a motor thereof and to efficiently collect energy during regeneration.
To deal with such a need, for example, Japanese Patent Laying-Open No. 2003-274565 discloses a hybrid type vehicle equipped with a power storage device including a secondary battery and a capacitor connected in parallel as an electric power supply source for a motor.
According to the disclosure, a power storage unit serves as a power supply including a secondary battery and an electric double layer capacitor connected in parallel. During constant-speed running and the like in which load variations in the vehicle are small, a controller operates an electric power generation motor using motive power of an engine to generate electric power, and charges the power storage unit with the generated electric power. The controller also discharges the power storage unit when the vehicle is driven by motive power of a drive motor, when an auxiliary machine for the vehicle is driven, and the like.
A vehicle equipped with a secondary battery serving as an electric power supply source for a motor is generally equipped with a cooling device to suppress an increase in a battery temperature due to heat generated inside the secondary battery during charge/discharge (see for example Japanese Patent Laying-Open Nos. 11-180168 and 2001-6651).
According to the disclosures, cooling wind generated by driving a cooling fan is supplied to a battery box housing a plurality of battery cells. The supplied cooling wind flows through a gap provided between the battery cells, and thereby the battery cells are cooled.
In a vehicle including a secondary battery and a capacitor as an electric power supply source for a motor as the one disclosed in Japanese Patent Laying-Open No. 2003-274565, internal heat generation also occurs in the capacitor as well as in the secondary battery, due to charge/discharge. Therefore, a cooling device is also needed for the capacitor.
The amounts of heat generated in the secondary battery and the capacitor during charge/discharge are different, depending on the magnitude of an internal resistance, the presence or absence of a chemical reaction, and the like. Accordingly, consideration has been given on a configuration in which a cooling device is provided separately for each of a secondary battery and a capacitor, and the amount of cooling wind to be supplied from the cooling fan is individually controlled based on the temperature of each of the secondary battery and the capacitor.
However, such a configuration requires to be provided with a plurality of cooling fans, resulting in an increase in the size of the entire cooling device, and thus the configuration may not be suitable to be mounted in a vehicle having severe mounting space constraints. Further, since the amount of cooling wind is controlled for each of the plurality of the cooling fans, there arises a problem that the control is complicated.
Furthermore, since the secondary battery and the capacitor have a temperature range suitable to maintain chargeable/dischargeable electric power, further improvement in the response of electric power supply to a motor is expected if these can be adjusted to have temperatures falling within the temperature range.
Accordingly, the present invention has been made to solve such a problem, and one object of the present invention is to provide a power supply unit including a cooling device that is smaller in size and has a simple configuration.
Another object of the present invention is to provide a power supply unit capable of adjusting temperature with a simple configuration.